#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

int main()
{
	double sum1 = 0.0;
	double sum2 = 0.0;
	double sum = 0;
	for (int i = 1; i < 100; i+=2)
	{
		sum1 = sum1 + 1.0 / i;
	}
	for (int j = 2; j < 101; j+=2)
	{
		sum2 = sum2 + 1.0 / j;
	}
	sum = sum1 - sum2;
	printf("%lf",sum );

	return 0;
}
